Making sand cores



Patented Apr. 28, 1931 PATENT OFFICE ALBERT arm, or HANOVER, GERMANY MAKING SAND GOBES I ll'o Drawing. Application filed April 5, 1928, Serial No. 287,799, and in Germany April 12, 1927.

My invention relates to coresfor metal cas'ting'molds and more particularly to a binder for cores -which consist principally or exclusively of pure quartz sand. e The cores of casting molds are either intended to remain in the mold in whichthey may have been formed,-having been dried or burned while in the mold, or they are dried independently of the mold after the core box l-has been removed. 7

My invention relates to cores of the latter kind which are dried independently'of the mold. Heretofore such cores were made of earth containing clay and loam which when mixed with water yield a plastic mass. Cores of any shape including complicated or undercut cores made from such earthy material will not collapse and will not undergo changes of form at normal temperature and in the'kiln. However, these cores involve certain drawbacks to wit 1. The core is not suificiently porous so that it is necessary to admix organic substances, such as dung, sawdlist and the like which impart porosity to the mass. It'is,

however, impossible to obtain in this manner uniform porosity so that the percentage of scrap is considerable.

2. The mass is not strong enou h and the 80 core must therefore be reinforcefby means ofiron bars or wires which are difiicult to remove from the finished casting.

3. In the kiln the core is burnt to the hardness of brick and must be removed from the casting by means of hammer and chisel or by neumatic tools. f

11 view of these and other drawbacks, cores made of earth are unsatisfactory. A core consisting principally or exclusively of purequartz sand, i. e. quartz grains of sub 'stantially uniform size, would be excellently suitable, but such cores could notbe' made heretofore for want of a suitable binder.

Self-supporting cores must stand at normal as the binders were not able to fulfill the ar,

ticular. requirements of casting practice as follows The binder must be ready for use without requiring any preparation, in order to enable the core molder to make any number of satisfactory cores bymixing a pre- 55- deter'inined quantity of quartz sand with a predetermined quantity of the binder. The binder must further remain unchanged for several months without its constituents separating.

The new binder according to this invention is a mixture of substances each of which has already been used separately orin combination with other substances, but none of these combinations aforesaid possesses the. properties required for a suitable quartz sand 2 binder.

The'new binder possesses the property of imparting to the core such initial strength that insertions are only required in exceptional cases while-on the other hand the core will immediately become disintegrated after casting and will flow from the casting in the condition of loose sand so that it is not necessary to remove it by special expedients.

My invention is based on the following considerations: In making a suitable core from quartz sand two binders are required, one of which should be soluble in water and the other in oil. The water-soluble binder must so impart to the core suflicient strength directly afterit has been molded, by evaporation of the water and consequent-incrustation of the surface of the'core. The oil-soluble binder renders the dried core proof against the moisture of the mold and imparts to it the re-' quired high strength during drying notwithstandin a minimum percentage of binder used. oth binders should bereduced to a V because any organic binder devel- 9o ops vapors or gases whichmay work damage to the casting. I

According to the present invention thetwo binders are combined in such manner as to yield astable mixture which is ready for use without 'preparation,- the composition 'of which does not change and the constituents of which do not, separate. 'This is efiected by combining the two constituents into a highly viscous 1 mixture which may have substanstored for many months without undergoing any change as to its composition and it is therefore possible to withdraw small doses of the binder from a cask during several months 1 without the portion which is used last, that is, I

the portion at the bottom of the cask, having other physical or chemical properties than the portions withdrawn at the beginning. Thus the core-maker need only admix per unit of weight of quartz sand the quantity of binder which has been determined once and for all, and he will always obtain a mass having the same plasticity and being invariable in shape at normal temperature and in the kiln. This is due to the fact that the binder will always and throughout its substance preserve those properties which were imparted to it initially. In this manner the principal drawback of existing binders of a similar character, to Wit, the tendency of their constituents to separate sooner or later without this becoming outwardly apparent, is eliminated.

Two substances have been found to be particularly suitable for making the new core binder, the water-soluble substance being sulfite liquor, the oil-soluble binder being a pitch, more particularly stearin pitch. By mixing these two substances in highly concentrated condition a mixture is obtained which is almost plastic, is invariable for any length of time and possesses all properties required for making quartz sand cores, as set out above.

For instance a sulfite liquor of 35 B'. which may still be concentrated if desired, is mixed with stearin pitch in the ratio of 30 to parts of sulfite liquor and 70 to 30 parts of stearin pitch. Good results will be obtained by employing equal quantities of the two constituents.

The density of the mixture is higher thanthe density of each constituent. Quartz sand cores made with this binder are so strong initally that they may be placed on a conveyer and carried from the coremakersstand to the kiln.

It is understood that I am not limited to any definite percentage of the two constituents, but the limits of percentages may be a 2. The minimum percentage of highly consistent water-soluble binder is such as required for obtaining a homogeneous mixture able properties of the crude materials, of the purpose for which the binder is used, and of the ambient temperature which varies with the season.

Heretofore no binder was known which is ready for immediate use and may be transported to the works in casks, of which the coremaker has only to add to the quartz sand a pretermined quantity in order to obtain a self-supporting core and Which does not undergo any changes during months.

Various changes may be made in the details disclosed in the foregoing specification without departing from the invention or sacrificing the advantages thereof.

I claim 1. A highly viscous core binder consisting of sulfite liquor and an oil-soluble pitch. I

2. A highly viscous core binder consisting of sulfite liquor and stearing pitch.

3. A metal casting core consisting of substantially pure quartz sand and a highly viscous mixture of sulfite liquor and stearin pitch.

In testimony whereof I alfix my si ature.

ALBERT ST HN. 

